There are presently available many methods for the in situ production of hydrocarbon gases from solid beds of carbonaceous material. One of the single greatest problems encountered in such methods is the effective supplying of air to burning sites. Once coal or another carbonaceous material has been ignited, it is essential that combustion be maintained. The prior art offers a variety of approaches to the problem. Examples of proposed solutions to the problems encountered with in situ gas production processes are found in U.S. Pat. No. 3,113,619, issued to A. D. Reichle on Dec. 10, 1963; U.S. Pat. No. 3,794,113 issued to L. K. Strange on Feb. 26, 1974; U.S. Pat. No. 3,997,005, issued to C. A. Komar on Dec. 14, 1976; U.S. Pat. No. 3,999,607, issued to R. E. Pennington et al on Dec. 28, 1976; U.S. Pat. No. 4,026,356, issued to L. Z. Shuck on May 31, 1977 and U.S. Pat. No. 4,054,393, issued to S. T. Fisher et al on Aug. 23, 1977.
The above patents propose a variety of solutions to the problems involved in the in situ production of gases in deposits of carbonaceous material, including (a) the inverse or counterflow injection of air to a combustion zone; (b) the use of a heated fluid to maintain a heated zone about a production well using steam in a direct combustion process; (c) the use of the natural fracture system in certain coals and the regulation of combustion supporting gas pressure; (d) the burning of coal over a limited area of a seam, collapsing overlying coal to form a rubblized zone, burning the rubblized zone and collecting the liquids and gases thus produced; (e) the forming of directional bores in coal beds using a laser beam to interconnect selected holes bored by conventional methods; and (f) the heating of a selected portion of a coal deposit using electrical induction techniques, whereby destructive distillation of the coal is effected. Most of the methods discussed above are either relatively complicated and expensive, or alternatively rely for success on the permeability of a carbonaceous deposit. In any event, a review of the literature and current methods for in situ production of gas in carbonaceous deposits makes it readily apparent that there is a need for a relatively simple, efficient method for the in situ production of gas in such deposits.